Loud speaker



Jan. 17, 1956 P. w. KLIPSCH 2,731,101

LOUD SPEAKER Filed June 6, 1952 By Paul W K/Losc/v Age/ifs United StatesThis invention relates to a loud speaker system, and more particularlysuch a system which combines direct radiation of high frequencies andcorner horn back-loading of the driver unit for low frequencies. Theinvention is especially useful in its application to loud speakersinstalled in the home for faithfully reproducing radio telephonicreception and phonograph records, to which use, however, the inventionis not limited.

Combined direct radiation of sonic high frequencies and indirect cornerhorn radiation of sonic low frequencies is not broadly new. In my PatentNo. 2,310,243, granted February 9, 1943, for Horn for Loudspeaker onesuch system is disclosed. Such apparatus gives faithful reproduction ofan extended bass range down through low C of the organ, and at the sametime accurate reproduction up to the highest audible sounds.Furthermore, the response of apparatus such as that disclosed in my saidpatent is smooth over its entire sonic range, giving complete coverageof the listening area wtihout either hot or dead spots. Such knownapparatus depends for its operation upon long acoustic passages andinternal baflies.

I have now found it possible to provide a combined direct radiation andcorner horn loud speaker system which gives an acoustic responseapproaching that of the apparatus disclosed in my aforesaid patent, andwhich at the same time is simple, inexpensive and of low bulk, and whichprovides low distortion and extended bass frequency range.

According to the present invention the entire horn is formed outside ofthe housing, and the housing itself forms a very simple acoustic lowpass filter which limits the bass range efficiency to an order ofmagnitude comparable with the middle range efficiency of the directradiator action. The housing forms a simple cavity which is unobstructedexcept for immersion of the driver unit therein. An acoustic inertance,in the form of an orifice or slit suitably formed in the housing, coactswith the cavity to provide the lowpass filter. The front panel of thehousing has a opening therein, and the driver unit is mounted in thecavity upon the front panel rearwardly of this front opening, throughwhich the treble sound radiation leaves the housing. The side panels ofthe housing extend convergingly rearwardly of the front panel to form,in conjunction with external proximate surfaces, the horn portions ofthe speaker, and to form with the front panel an acoustic capacitance inthe form of an unobstructed cavity. At the rear of the cavity anacoustic inertance is provided in the form of a constricted opening ororifice, through which the bass frequency sound enters the horn. Thusthe cavity and the orifice form the low-pass filter for the bassfrequency sound between the driver unit and the born.

The invention is shown by way of illustration in the accompanyingdrawings, in which Fig. 1 is a horizontal section taken through aspeaker constructed and arranged according to the invention, togetherwith the wall angle providing the proximate suratent faces forming theexternal horn, the section being taken on the line I-I of Fig. 2.

P Fig. 2 is a front elevation of the speaker shown in Fig. 3 is avertical section taken through the speaker shown in Figs. 1 and 2, thesection being taken on the line III-III of Fig. 2, and

Fig. 4 is a horizontal section, similiar to that shown in Fig. 1illustrating a different type of speaker also con structed and arrangedaccording to the invention.

In the embodiment of the invention which is illustrated in Figs. 1, 2and 3 of the drawings, there is shown a generally prismatic-shapedspeaker or housing 10 symmetrically disposed with respect to proximatesurfaces 11, 11 which are provided as by the walls of a room meeting ina corner at The speaker 10 comprises a housing, an important part ofwhich is a front panel 12, having an opening 13 therein between its sideedges. Side panels 14, 14 are joined at their forward edges to the frontpanel at its side edges, and extend convergingly rearwardly therefrom atequal angles thereto and at an acute angle to one another. Coplanarpanels 15, 15 extend inwardly from the rear edges of the respective sidepanels to a slot or orifice 16 in the rearmost part of the housing. Ashere shown the slot or orifice 16 is a slot extending from top to bottomof the housing.

A bottom panel 17 closes the lower end of the cavity 18 formed by thefront panel 12, the side panels 14, 14 and the rear coplanar panels 15,15; and a top panel 19 closes the top of the cavity so formed. Thus, thecavity 18 constitutes an acoustical capacitance or resonance cavity,completely closed except for the opening 13 in the front panel and theslot or orifice 16 formed at the rear center of the cavity between therear coplanar panels 15, 15.

A cover 20 is fixed to the upper surface of the top panel 19, and itsextent is such as to meet the walls or proximate surfaces 11, 11 whenthe speaker is suitably placed. Thus the cover 20 cooperates with thewalls to form horn sections 21 and 22 between the side panels 14, 14 andthe proximate surfaces 11, 11. The lower limit of the horn sections is,of course, defined by the floor.

The driving unit 23 of the speaker is mounted upon the front panel 12,rearwardly of the opening 13, therein, within the cavity 18. Thus thedriving unit is immersed in the cavity, which is otherwise unobstructed,and closes the opening 13, through which is treble sound of the unitleaves the speaker. The bass frequencies of the driving unit enter thecavity 18, pass through the low pass filter formed by the acousticcapacitance of the cavity and the acoustic inertance of the slot 16 andthence enter the throat of the horn, passing outwardly therefrom throughthe two horn sections 21, 22. It has been found that best results areobtained when the area of the slot 16 is appreciably smaller than thatof the horn throat.

The speaker has been built experimentally in a size thirty-six incheshigh. The response of such speaker has been found to be very good downto 35 cycles, and produces usable fundamental output down to 30 cycles.In the speaker referred to, the cutoff is 30 cycles, the wave length is450 inches or substantially twelve times the height of the speaker, andthe acoustic cut-oif is about cycles. The side panel convergence hasbeen designed to provide a horn cut-01f of the order of a wave lengthtwelve times the height of the housing, and this design is such that thecavity-slot low-pass acoustic filter cut-off frequency is of the orderof four times the frequency of the horn cut-off.

The driving unit 23 may be of any known or convenient form, and goodresults have been obtained with such units known as Alice 6043, JensenG-6l0, University 6201, and other coaxial and simple driver systems. Insuch tests it has been observed that at least one octave more of cleanfundamental bass output has been obtained than that which can berealized with ordinary baffle cavities.

As illustrated in Figs. 1, 2 and 3, the front panel 12 is a compositepanel comprising a central element in which the opening 13 is formed andupon which the driving unit is mounted, and coplanar elements 25 and 26on either side of the central element to which the side panels 14, 14are fixed. The central element 24 of the front panel 12 is made unitarywith the coplanar elements 25 and 26 by means of longitudinal strips 27and. 28, the central element, the coplanar elements and the longitudinalstrips extending from top to bottom of the front panel. The arrangementdescribed is found to give desirable resonance to the speaker 10.However, whether or not such composite construction is employed, it hasbeen found that the customary sound-deadening material is not needed inspeakers constructed and arranged according to the invention.

It is to be noted that the opening 13 is positioned as high as possiblein the front panel to effect frontal direct radiation in a high regionof the speaker which is more nearly on the level of the ears of thelistener than would be the case were the driver unit positioned at alower level in the speaker.

The loud speaker system herein described combines direct radiatorperformance for high frequencies and corner horn back loading of thedriving unit for base frequencies. The acoustic low-pass filter isinterposed between the back of the driving unit and the throat of thehorn, whereby the bass response is flattened. The entire horn is outsideof the housing, and the entire housing space is devoted to cavity, withthe exception of the space required for immersion of the driver unittherein. The low-pass filter, with a gradual slope, feeds back to thehorn throat which is roughly proportional to the bass wave length.Accordingly, the sound output remains reasonably constant.

From the horn throat, immediately back of the slot or orifice 16, thesound wave expands in the horn sections 21 and 22; and the horn designis deliberately made so that the efficiency will drop with frequency, inorder that the combined operation of the horn and the acoustic filtermay offer a reasonably flat response in the bass frequency range and inoffering bass output of approximately the same intensity as thatradiated through the opening 13 in the front panel 12.

For the reasons just stated the horn is made short and a of smallermouth size than would ordinarily be considered good design for a fullyhorn loaded loud speaker system. As a result of the decreased horn size,combined with the described simple acoustic filter, a horn efficiencywhich is approximately proportional to frequency over a two-octave rangeis realized.

In the embodiment which is illustrated in Fig. 4 a similar speaker 16::is shown. However, in this form of speaker the front panel 12a is not ofcomposite construction and the side panels 140, 14a extend directlyrearwardly of the front panel to form between them a slot or orifice16a; and no coplanar panels 15, 15 are employed in forming the speaker.The resulting cavity 18a is slightly smaller than the cavity 18 formedby the speaker illustrated in Figs. 1, 2 and 3 but the construction anduse of the speaker 10a is otherwise the same.

A loud speaker system constructed and arranged according to theinvention gives a wider tonal range than can be obtained from simplebattles and resonated enclosures of comparable size. It providesadequate loading of the driving unit diaphragm near the diaphragmsuspension, effecting reduction of diaphragm excursion with resultantreduction in diaphragm distortion. Furthermore, reduced intermodulationdistortion results from reduced diaphragm excursion, and the presentinvention thus reduces such inter- 4 modulation distortion. It isparticularly to be noted that reduction of diaphragm excursion iseffected by imposing radiation resistance, so that bass output isincreased rather than reduced. Such results are realized in simple andinexpensive manner in a speaker of small volume.

The forms of the invention here described and illustrated are presentedmerely as examples of how the invention may be applied. Other forms andembodiments coming within the proper scope of the appended claims will,of course, suggest themselves to those skilled in the art.

I claim:

1. In a corner horn loud speaker, a prismatic-shaped housing forsymmetric location in a corner formed by the walls of a room to providea length of horn between the housing and the room walls, said housingforming a closed cavity and comprising a front panel having an openingtherein to exhaust treble sounds from a driver unit mounted upon saidfront panel at the opening therein, said housing also comprisingrearwardly converging side panels forming a slot-like port to exhaustbass frequencies into the throat of the horn formed between said housingand the room Walls.

2. A speaker according to claim 1, in which the size of the cavity andslot-like port are coordinated to form a lowpass filter.

3. In a speaker according to claim 1, side panel convergence providing ahorn cut-off of the order of a wave length twelve times the height ofthe housing, and a cavity-slot low-pass acoustic filter cut-off of afrequency of the order of four times the frequency of the horn cutofif.

4. A corner horn loud speaker comprising a driver unit, in combinationwith a cavity-slot acoustic low-pass filter fed by one side of saiddriver unit, and an acoustic horn external to said filter, a part ofwhich is formed by said filter, said filter being constructed andarranged to feed the throat of said acoustic horn.

5. In a corner horn speaker system for use with a direct radiator driverunit for treble frequencies and a corner horn bass loading of one sideof the driver unit for bass frequencies; a prism-shaped housingconstructed and arranged to form a length of horn between said housingand the walls forming a corner in a room, said housing providing anacoustic capacitance in the form of a cavity therein, said housinghaving therein an acoustic inertance in the form of an orificepositioned to feed sound waves into the throat of the horn formedbetween said housing and the room walls, and the acoustic capacitanceand acoustic inertance in said housing providing a low-pass filterbetween the driver unit and the horn throat.

6. A corner horn loud speaker according to claim 1 wherein the slot isappreciably smaller in area than the throat of the horn.

7. A corner horn loud speaker according to claim 5 wherein area of theorifice is appreciably smaller than that of the throat of the born.

8. A loud speaker of the corner horn back-loading type comprising afront panel having an opening therein between its side edges, sidepanels joined at their forward edges to the side edges of said frontpanel extending convergingly rearwardly at equal angles thereto and atan acute angle to one another to define with said front panel anunobstructed cavity and to form an inertance opening of small size attheir rearmost points of convergence, and a driving unit mounted uponsaid front panel rearwardly of the opening therein within the cavitydefined by said front panel and said side panels.

9. A loud speaker of the corner horn back-loading type comprising afront panel having an opening therein between its side edges, sidepanels joined at their forward edges to the side edges of said frontpanel extending con ergingly rearwardly at equal angles thereto and atan acute angle to one another to form a slot at their rear edges and todefine with said front panel an unobstructed cavity. and a driving unitmounted upon said front panel rearwardly of the opening therein withinthe cavity dc fined by said front panel and said side panels.

10. A loud speaker of the corner horn back-loading type comprising afront panel having an opening therein between: its side edges, sidepanels joined at their forward edges to the side edges of said frontpanel extending convergingly rearwardly at equal angles thereto and atan acute angle to one another, coplanar panels joined to the rear edgesof said side panels and extending toward one another to form a slot attheir unconnected edges, said side panels and said coplanar panelsdefining with said front panel an unbaffled cavity, and a driving unitmounted upon said front panel rearwardly of the opening therein withinthe cavity defined by said front panel and said side panels.

11. A loud speaker cabinet wherein side panels thereof coact to providehorn sections with proximate surfaces fixed at substantially 90 to oneanother to form a corner in which the cabinet is symmetrically disposed,said cabinet comprising: a front panel; side panels extending reawardlyfrom the side edges of said front panel at equal angles thereto and atan acute angle to one another; a top panel fixed to the upper edges ofsaid front panel and said side panels; and a bottom panel fixed to thelower edges of said front panel and said side panels; said front panel,said side panels, said top panel and said bottom panel defining anunobstructed cavity; and said side panels forming at their rearmostpoints of convergence an inertance opening of small size to admit lowfrequencies to the horn beyond said cabinet.

12. A loud speaker cabinet wherein side panels thereof coact to providehorn sections with proximate surfaces fixed at substantially 90 to oneanother to form a corner in which the cabinet is symmetrically disposed,said cabinet comprising: a front panel; side panels extending rearwardlyfrom the side edges of said front panel at equal angles thereto and atan acute angle to one another;

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a top panel fixed to the upper edges of said front panel and said sidepanels; and a bottom panel fixed to the lower edges of said front paneland said side panels; said front panel, said side panels, said top paneland said bottom panel defining an unobstructed cavity; and said sidepanels forming at their rearmost points of convergence a slot extendingthe entire height of said cabinet to admit low frequencies to the hornbeyond said cabinet.

13. A corner horn loud speaker comprising a prismatic shaped housing forsymmetric location in a corner formed by the walls of a room to providethe entire horn of the speaker between said housing and such walls, saidhousing comprising a hollow shell bounded by a substantially plane frontpanel and side panels converging rearwardly therefrom, the front panelof said housing having an opening therein to exhaust treble sounds froma driver unit mounted upon the front panel at the opening therein andimmersed in the hollow shell formed by said housing, and the side panelsof said housing converging rearwardly therefrom, said housing having avertical slot formed centrally of its rear extremity to exhaust lowfrequency tones into the corner formed by the walls of the room.

References Cited in the file of this patent UNITED STATES PATENTS2,310,243 Klipsch Feb. 9, 1943 2,337,213 Topping Dec. 21, 1943 2,373,692Klipsch Apr. 17, 1945 OTHER REFERENCES Publication (II) ElementsAcoustic Engineering by Olson, 2nd edition, pages 208-209. (Copy in U.S. Patent Office TK5981.05.)

McProud: A New Corner Speaker Design," article in Audio Engineering,January 1949 (pages 14-17 and 39).

